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Патент USA US3099838

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July 30, 1963
F. w. KELLEY, JR
3,099,328
1 PROTECTIVE CIRCUITRY AND INDICATING MEANS FOR RECTIFIER SYSTEMS
Filed July 17, 1958
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INVENTOR.
Fred W. KeHe'yJr.
BY Km 6. M
H is AHorney
July 30, 1963
F. w. KELLEY, JR
3,099,828
PROTECTIVE CIRCUITRY AND INDICATING MEANS FOR RECTIFIER SYSTEMS
Filed July 17, 1958
'
2 Sheets-Sheet 2
%
Fig. 3
Loud
INVENTOR.
Fred W. Kelley. Jr.
BY Wm add‘
His A?orney
ice
3,099,828
Fred W. Kelley, Jr., Lynchhurg, Va., assignor to General
Electric Company, a corporation of New York
Filed July 17, 1958, Ser. No. 749,176
14 Claims. (Cl. 340-—248)
Patented July 30, 1963
2
1
PROTECTIVE CIRCUITRY AND INDICATING
MEANS FUR RECTIFIER SYSTEMS
3,099,828
A further object of my invention is to provide means for
also indicating that a fuse has blown in the recti?er leg.
Further objects and advantages of my invention will
become apparent as the following description proceeds.
Brie?y stated, in accordance With one embodiment of
my invention, I provide circuit means for impressing a
voltage across each recti?er cell in opposition to and of
less potential than the inverse voltage normally appearing
My invention relates to recti?er systems which normally
across the recti?er cell. Recti?ers are provided for block
operate at a high voltage and more particularly to protec 10 ing the ?ow of current through the circuit means during
tive circuitry and indicating means vfor such recti?er
normal operation and yet allowing a current to ?ow when,
systems.
due to the shorting of a cell, the impressed'voltage across
In many large recti?er installations, a great number of
a cell exceeds the inverse voltage acres the cell. An im_
rectifying legs are individually fused and are connected
pedance, whose value is changed upon a ?ow of current
in parallel to form a recti?er bank. The recti?er banks 15 through the circuit means, is included, and an indicating
may be individually used, as in a single phase half-wave
means is associated with the impedance to effect an indi
rectifying system, or they may ‘be used in multiple, as in
cation of a failed cell when the value of the impedance
a single-phase full-wave system or a polyphase system
wherein each recti?er bank is connected to one of the
changes.
Since many of the large recti?er installa
While the speci?cation concludes with claims particu
larly pointing out and distinctly claiming the subject mat
tions operate at a high voltage, it is often necessary that
each recti?er leg consist of a number of recti?er cells in
series in order to yadequately handle the high inverse
ter which I regard as my invention, it is believed that
my invention will be better understood ‘from the follow
ing description taken in connection with the accompany
voltage developed across the recti?er leg. The usual fail
ing drawings in which:
ure of a recti?er cell is in the form of a short circuit across 25
FIGURE 1 is a schematic Wiring diagram showing an
embodiment of my invention incorporated with a recti?er
phase legs.
the cell which consequently results in a higher inverse
voltage being ‘developed across each of the remaining
recti?er cells in the leg. In order to prevent the failurte
of the remaining cells, suitable protective circuitry is nec
leg;
FIGURE 2 is a schematic wiring diagram showing a
different embodiment of my invention incorporated with
essary so that the failure of one or more recti?er cells 30 a recti?er leg; and
may ‘be noted and the recti?er leg disconnected to allow
replacement of the defective cell.
In some prior forms of protective circuitry, sensing re
FIGURE 3 is a schematic diagram illustrating a vfurther
modi?cation of my invention as applied to a plurality
of recti?er legs.
The recti?er system of FIGURE 1 comprises a recti?er
cells in a recti?er leg. In one ‘form of installation, each 35 leg, shown generally at 1, an AC. voltage source 2 in
sensing relay includes the control coils each of which is
series with the recti?er leg, and a load 3 in series with
connected across a different recti?er cell in the recti?er leg.
both the recti?er leg and the AC. source. While I have
The coils are connected so as to act in opposition to each
shown only one recti?er leg in this recti?er system, it
other in order to cancel out each other’s effect on the relay
should ‘be understood that a plurality of recti?er legs may
when both recti?er cells are in good operating order. 40 be used in parallel to achieve the necessary current rating.
Upon failure of one of the recti?er cells, its correspond
It is fmther ‘apparent that in place of the single phase
ing coil becomes shorted out and the remaining coil then
half-Wave recti?er system shown, a polyphase full-wave
picks up the relay in order to give an indication that a cell
recti?er system, or other variation of a recti?er system,
has failed. This arrangement has not proved to be com
may be used and this would still be within the concept of
pletely reliable due to the fact that the inverse impedances
my invention.
of the individual recti?er cells are often found to vary
As shown in FIGURE 1, rectifying leg 1 includes a
considerably from sell to cell for normal manufacturing
plurality of recti?er cells 4, 5, 6, and 7, connected in
tolerances. This leads to imperfect operation of the relays
series in order to ‘distribute the high inverse voltages
since the voltage across one coil is often su?iciently differ
developed across the leg. In actual practice, the inverse
ent from the voltage across the other coil to cause the
impedance of each cell in a vgroup of recti?er cells in
relay to pick up and give an erroneous indication. Addi
series may vary considerably so that it often is necessary
tionally, the cost of each of the sensing relays is signi?
to
provide means for balancing the various inverse impe
cant and since the great number of them must be used
dances
to more evenly distribute the inverse voltage
in a large rectifying system the expense involved becomes
55 amongst the cells. In order to accomplish this, a plu
almost prohibitive.
rality of ‘balancing resistors 8, 9, 10, and 11, which are
Accordingly, one object of my invention is to provide
preferably of equal value, are each connected in parallel
improved protective circuitry and indicating means for
lays are used to indicate the failure of one of the recti?er
a recti?er system.
with their corresponding recti?er cells 4—7, respectively.
It is apparent that should recti?er cells 4~7 be selected and
means for indicating the failure of a recti?er cell in a 60 matched so as to have substantially equal inverse impe
A further object of my invention is to provide improved
recti?er leg.
Another object of my invention is to provide an im
proved arrangement for remotely indicating the failure of
a recti?er cell in a recti?er leg.
dances, the necessity for balancing resistors 8-11 would
be obviated; however, this normally would prove to be
a costly procedure and the balancing resistors should
preferably be included.
3,099,828
3
My invention incorporates circuitry which will ener
4
ing the conducting half cycle of the recti?er leg, the
gize an indicating means when the ratio of the inverse
blocking recti?ers are non-conductive since they are
voltage of any recti?er cell to the inverse voltage of the
recti?er leg departs from a predetermined minimum value,
polarized in opposition to the voltages developed in the
secondary windings during this part of the cycle and
the minimum value being chosen so as to compensate for
individual variations due to manufacturing differences.
In order to provide means for sensing and comparing the
these voltages exceed the forward voltage drops of their
corresponding recti?er cells. During the blocking half
cycle of the recti?er leg, although the blocking recti?ers
inverse voltage developed across the recti?er leg with the
are polarized so as to allow current flow through the
inverse voltages developed across the recti?er cells, a
secondary windings at this time, current may ?ow only if
transformer, shown generally at 12, is provided. Trans 10 the voltage across the particular secondary winding ex
‘former 12 includes a primary winding 13 and a plurality
ceeds the inverse voltage developed across its correspond
of secondary windings 14-17‘. One side of primary wind
ing recti?er cell. Since, during normal operation, the
ing 13 is connected through a capacitor '18‘ to one side
voltage across each secondary winding will be lower than
of recti?er leg 1. The opposite side of primary winding
the inverse voltage of its corresponding recti?er cell in
13 is connected through a resistor 19 to the other side of 15 an amount dependent upon the turns ratio between the
recti?er leg 1 to form a completed A.C. circuit across the
primary and secondary windings of the transformer, no
recti?er leg. Capacitor 18 is chosen so as to block the
current flow will take place in the secondary windings
?ow of DC through the primary winding of the trans
former and yet provide a low impedance to the ?ow of
and the transformer primary winding '13 will present a
high impedance to the ?ow of current in the primary wind
A.C. through this circuit.
20 ing circuit. This results in a relatively high voltage drop
It is apparent that the inverse voltage developed across
across the primary winding and a corresponding rela
the recti?er leg will be impressed across the primary wind
tively low voltage existing across series resistor 19.
ing A.C. circuit and will be, essentially, divided between
The condition of operation of the protective circuitry
the primary winding and its series resistor. It is also ob
and indicating means may be summarized as follows.
vious that should the impedance of transformer primary 25 During normal operation the primary winding A.C. cir
winding 13 change, the voltage drop across the primary
cuit, comprising primary winding 13, series resistor 19,
winding will change in one direction and, consequently,
and capacitor 18, has an A.C. voltage impressed across
the voltage drop across series resistor 19‘ will change in
it which corresponds to the inverse voltage existing across
the opposite direction since the eifective voltage across the
recti?er leg 1; the voltage drops across primary winding
entire series A.C. circuit does not vary.
30 13 and its series resistor 19‘ are such that the indicating
In order to utilize the change in voltage across series
lamp 20 will not ?re; and each of the secondary winding
resistor 19 to activate an indicating means, neon indicat~
14~17 effectively re?ects an open circuit condition into
ing lamp 20 and its current limiting resistor 21 are
shunted across the series resistor 19‘. Under normal
operating conditions, when the recti?er cells 4-7 are in
good operating order, the.voltage across series resistor
19 will be below the ?ring voltage of neon indicating lamp
20; however, when a recti?er cell shorts, the voltage across
the primary winding 13 will decrease due to a lowering of
the primary winding 13. In this situation the ratios of
the inverse voltage of each recti?er cell to the inverse
voltage of the recti?er leg are all above a predetermined
value and the circuitry senses this condition.
Upon the failure of a recti?er cell, in this case assuming
that recti?er cell 4 becomes shorted, it is apparent that
the voltage induced in secondary winding 14- will then
the impedance of this winding in a manner to be more 4:0 cause a cur-rent to ?ow through this winding on ‘alternate
fully described hereinafter. In consequence of this, the
voltage across series resistor 19‘ will increase to a value
half cycles when the recti?er leg .1 is in its blocking con
dition. This results in a lowering of the impedance of
greater than that required to ?re the indicating lamp and,
primary winding 13 in the transformer primary winding
as a result, the lamp will ‘give ‘an indication of a shorted
recti?er cell. It is apparent that various other means may
be used to sense the voltage change across series resistor
19 to give an indication that a cell has shorted. A relay
A.C. circuit. In consequence of the lower impedance of
arranged to energize an alarm or trip the supply circuit
to the recti?er system could be used in place of the neon
indicating lamp 211. Such a relay would be one in which
the voltage across series resistor 19 under normal condi~
tions would be insuf?cient to energize it, but which would
be energized by the higher voltage existing when a recti~
?er cell has shorted.
In order to sense that a recti?er cell has shorted and,
in consequence of the shorting, has changed the values
of the Voltages existing across primary winding 13 and
series resistor 19, each of the secondary windings 14—17
of transformer 12 is connected through its corresponding
blocking ‘recti?er 22—25 to its corresponding recti?er cell 60
primary winding 13, the voltage drop across series resistor
19 increases to the point where neon indicating lamp 20
?res and an indication of a shorted recti?er cell is given.
In this situation, one of the ratios of cell inverse voltage to
leg inverse voltage has fallen below the predetermined
value and the circuitry senses this condition.
Thus, by utilizing my invention, an improved arrange
ment for protecting a recti?er system and indicating the
failure of a recti?er cell is achieved.
In the embodiment shown in FIGURE 2, a fuse 26
has been added in series with the recti?er cells of recti
her leg 1. In addition, a second sensing and indicating
circuit comprising potentiometer 27, partially shunted by
neon indicating lamp 28 which is in series with current
limiting resistor 29, has been added to the components
4-7, respectively. The turns ratio between the primary
winding 13 and each of the various secondary windings
discussed in the FIGURE '1 embodiment in order to pro
vide means for indicating the condition of fuse 26. The
numbering system used in FIGURE 1 has been preserved
14-17 is chosen so that the voltage induced in each
secondary winding as a result of- the A.C. voltage im
in FIGURE 2 wherein components which are the same
as those in FIGURE 1 have similar numerals assigned
pressed across the primary winding 13‘ will be lower than 65 to them.
the inverse voltage appearing across each corresponding
During normal operation, with no recti?er cells shorted,
recti?er cell when the cell is in good operating order. This
the operation of the circuit in FIGURE 2 will be similar
is done to insure that each secondary winding will ef
to that of FIGURE 1; however, should a recti?er cell
fectively sense a substantially “open circuit” across its
winding and re?ect this condition back into the primary
winding of the transformer when the recti?er cells are in
'good condition.
The blocking recti?ers 22-25 will normally have no
current ?owing. through them during either the conduct
ing or the blocking half cycle of the recti?er leg 1. Dur
fail, the ?ring of indicating lamps 20‘ and 28 becomes
‘dependent in some measure upon whether or not fuse
26 has blown. In (order to insure that indicating lamp
20 will be lit at all times where a recti?er .cell has failed
and the fuse 26 is in good condition, the indicating
lamp 2%, which is similar to indicating lamp 2%}, and
its current limiting resistor 29 are shunted across a por
3,099,828
6
5
?er banks may be located ‘over a substantial area.
tion of potentiometer 27. With this arrangement it is
apparent that the potentiometer may be adjusted so that
In
such a large installation it would be difficult to ade
indicating lamp 28 will require a slightly higher voltage
quately supervise the many indicating lamps distributed
to exist across the parallel combination of resistor 19
and potentiometer 27 before it ?res than does indicat
throughout the system and consequently a shorted cell
might go undetected for a substantial time. With the
remote indication system of this embodiment all of the
ing lamp 20. This insures that lamp 2%} will be ener
indicators may be brought to a single panel and ade
quately supervised by a single person in order to prevent
multiple failures upon the failure or a single cell.
Igized at all times when a recti?er cell has shorted and
rinse .26 is in good condition. Alternatively, instead of
using potentiometer 27 to cause indicating lamp 2% to
?re at a higher voltage, neon indicating lamp 28 may
be chosen so that its initial ?ring voltage is higher than
that of indicating lamp 20. It would then be connected
While I have shown and described a number of em
bodiments of my invention, it would be obvious to those
skilled in the art that various changes and modi?cations
may be made without departing from my invention in
across a resistor rather than the potentiometer 27 in or
its broader aspects, and I, therefore, aim in the ap
der to achieve the same result of a positive ?ring of
indicating lamp 2h when a recti?er cell has shorted and 15 pended claims to cover all changes and modi?cations as
fall within the true spirit and scope of my invention.
the fuse 26 is in good condition.
What I claim as new and desire to secure by Letters
It is possible that indicating lamp 28 may ?re, in
Patent of the United States is:
addition to lamp 20, when fuse 26 is in good condition
1. In combination, a plurality of recti?er legs connected
since the voltage developed across both lamps may be
high enough to ?re both lamps during the time it takes 20 in parallel to form ‘a recti?er bank which is subject to a
high inverse voltage during the blocking portion of an
lamp 20 to ?re; however, in the event that fuse 26 blows,
alternating current cycle, each recti?er leg including a
it is apparent that the AC. circuit through primary wind
plurality of recti?er cells connected in series; and a pin
ing 13 can no longer be maintained through indicating
rality of means each connected to a different ‘one of said
lamp 20 and therefore this lamp will be de-energized and
only indicating lamp 28 will remain lit. In this em 25 recti?er legs for detecting the failure of at least one of
the recti?er cells therein, each of said means comprising:
bodiment, therefore, it is apparent that should either
a transformer having ‘a primary Winding connected across
lamp 20, or both lamps 20 and 28 be lit, it would be
the corresponding recti?er leg and a plurality of second
indicative of the fact that ‘fuse 26 is in good operating
ary windings each connected across ‘a corresponding rec
louder; however should only lamp 28 be lit and lamp ‘20
be extinguished it would ‘be indicative of the fact that 30 ti?er cell in said corresponding leg, a blocking recti?er
in series with each of said secondary windings for nor
the fuse 26 has blown.
mally maintaining said windings in a substantially open
The embodiment shown in FIGURE 3 may be used
circuit condition, and indicating means remote from said
with a rectifying system, including a recti?er bank com
legs and connected in series with each of the primary
prised of a plurality of recti?er legs, where it is desired
that a remote indication of the shorting of a recti?er cell 35 windings of said cell failure detecting means and re
sponsive to a substantial variation in the ratio of the
be given. The numbering system used in FIGURES l
inverse voltage across any one of said legs and the inverse
and 2 has been preserved in FIGURE 3 wherein com
voltage across each of the cells therein for indicating
ponents which are the same as those in the previous
that a recti?er cell has failed, and means for selectively
?gures have the same numerals assigned to them. It may
be seen that the essential components associated with 40 disconnecting said primary windings from said indicating
means whereby deactivation of said indicating means is
each recti?er leg have been renumbered with the letter
effective to indicate the recti?er leg containing the failed
“a,” “b,” “c,” to indicate that they are similar compo
cell.
nents to those of the previous ?gures as they appear
2. In combination with a recti?er leg having a plurality
in the various recti?er legs of the new embodiment. 45
of recti?er cells connected in series, means for detecting
While I have shown the recti?er banlr, in this instance,
the failure of at least one of said recti?er cells com
as comprising ‘only three recti?er legs and their protective
prising: ‘a transformer having ‘a primary winding con
circuitry in order to make the drawing more compre
nected ‘across said recti?er ‘leg and a plurality of secondary
hensible, it should be understood that the recti?er bank
may include many more legs than are actually shown. 50 windings, said secondary windings each being connected
across a corresponding recti?er cell; a blocking recti?er
The recti?er legs 1a, 1b, and 1c, are connected across
in series with each of said secondary windings; impedance
the positive and negative buses 30 and 31, respectively,
of the recti?er bank. The indicating lamps 20a, 20b,
means and impedance means including ‘an indicating device
connect-ed in series with said primary winding to form a
and 20c, are connected through remotely located nor
mally closed switches controlled by push buttons 32, 33,
and 34, respectively, to a common resistor 35, a series
indicating lamp 36 and- back to the positive bus 30.
With this con?guration, should a recti?er cell fail in one
of the recti?er legs the corresponding indicating lamp
20a, 20b, or 200 will ?re.
In addition to one of these indicating lamps ?ring,
55
series circuit \across said recti?er leg, said series circuit
providing voltage drops across said primary winding and
said indicating means having a predetermined ratio dur
ing normal operation of the recti?er leg; each of said
secondary windings being responsive to the failure of a
recti?er cell for changing the ratio of the voltage drops
across the said primary Winding and said indicating means
to activate said indicating means.
3. In combination with a recti?ed leg. having a plurality
an indication at a remote point that one of the recti?er
of recti?er cells connected in series, means for detecting
cells has failed. In order to determine at the remote sta
tion which recti?er leg contains the failed cell, the push 65 the failure of at least one of said recti?er cells comprising:
a transformer having a primary winding and a plurality
buttons 32-34 may be selectively depressed until the re
remote indicating lamp 36 will also be energized to give
of secondary windings, said secondary windings each
mote indicating lamp 36 is de-energized. When the lamp
being connected across a corresponding recti?er cell; a
36 is tie-energized‘, it will be apparent that the recti?er
blocking recti?er in series with each of said secondary
leg containing the rfailed- cell is the one that is in cir
cuit with the push button whose depression effected de 70 windings for normally maintaining said windings in a
substantially open circuit conditions; and impedance
energization of lamp 36. For example, suppose that the
means connected in series with said primary winding to
lamp 36 is extinguished when the push button 32 is de
form a series circuit, said circuit being connected across
pressed. ‘It will then be known that the failed recti?er
said recti?er leg, vand indicating means connected in shunt
cell is located in recti?er leg In. It is apparent that in
with said impedance means for responding to changes
an extremely large recti?er installation, the various recti
3,099,828
'5’
in the impedance of said primary winding in response
3
and said series resistor during normal operation of the
to a flow of current in said secondary windings during
the blocking half cycle of said recti?er leg.
4. The combination of claim 3 wherein the turns ratio
between the primary winding and each of the secondary
windings of the transformer is such that the inverse volt
recti?er leg; indicating means including a neon indicating
lamp and a current limiting resistor, said indicating means
being shunted across said series resistor, said neon indi
age appearing across each recti?er cell exceeds the voltage
each of said secondary windings for normally maintaining
induced in its corresponding secondary winding during
normal operation.
cating Ilamp ‘being de-energized during normal operation
of said recti?er cells; a blocking recti?er in series with
each of said secondary windings in an open circuit condi
tion, each of said blocking recti?ers being polarized in
5. The combination of claim 4 wherein said blocking 10 such a manner with respect to its corresponding recti?er
cell and secondary winding that current will ?ow there
flow therethrough only when the voltage induced in a
through :only When the voltage induced in its corresponding
secondary winding exceeds the inverse voltage across its
secondary winding exceeds the inverse voltage across its
corresponding recti?er cell.
corresponding recti?er cell due to the failure of that recti
6. The combination of claim 3 wherein each of said 15 ?er cell, said current ?ow being effective to decrease the
recti?er cells is shunted by a balancing resistor for dis
impedance of said transformer primary winding whereby
tributing the inverse voltage across the recti?er leg evenly
the voltage drop across said series resistor is increased
amongst the recti?er cells.
and said neon indicating lamp is energized.
7. In combination with .a recti?er leg having a plurality
11. In combination with a recti?er leg having a plural
of recti?er cells connected in series, means for detecting
ity of recti?er cells connected in series, means for detect
recti?ers are polarized in such a manner that current will
the failure of at least one of said recti?er cells comprising:
ing the failure of at least one of said recti?er cells com
a transformer having a primary winding and a plurality of
prising: a transformer having a primary winding connected
secondary windings, said secondary windings each being
across said recti?er leg and a plurality of secondary wind
connected across a corresponding recti?er cell; indicating
ings, said secondary windings each being connected across
means in series "with said primary Winding to» form a 25 a corresponding recti?er cell for impressing a voltage
series circuit, said series circuit being connected across
across each cell in opposition to the inverse voltage ap
said recti?er leg and providing predetermined voltage
drops across said primary winding and said indicating
pearing thereon; means for normally maintaining said
secondary windings in a substantially open circuit condi
means during normal operation of the recti?er leg; a block
tion and responsive to the failure .of a cell to allow cur
ing recti?er in series with each of said secondary windings, 30 rent ?ow through the secondary winding corresponding
the shorting of a recti?er cell operating to decrease the
to the failed cell; and indicating means including an im
voltage drop across said primary winding and corre
pedance device connected in series with said primary wind
spondingly to increase the voltage drop across said indicat
ing and responsive to changes in impedance of said pri
ing means whereby said voltage drop across said indicat~
mary winding due to current ?ow in at least one of said
ing means ‘exceeds the voltage required to actuate said 35 secondary windings for effecting ‘an indication of a failed
indicating means.
recti?er cell.
8. In a recti?er bank which is subject to a high inverse
12. In combination with a recti?er ‘leg having a plural
voltage during the blocking portion of an alternating
ity of recti?er cells connected in series, means \for detecting
current cycle and which includes a plurality of recti?er
the failure of at least one of said recti?er cells compris
legs connected in parallel across the recti?er bank, each 40 ing: a transformer having a primary winding connected
recti?er leg including a plurality of recti?er cells con
across said recti?er leg and a plurality of secondary Wind
nected in series, means for detecting the failure of at
ings, said secondary windings each being connected across
least one of the recti?er cells in a recti?er leg comprising:
a corresponding recti?er cell; a blocking recti?er in series
a plurality of transformers each having a primary wind
with each of said secondary windings for normally main
ing and a plurality of secondary windings, said secondary 45 taining said windings in a substantially open circuit condi
windings of each transformer each being connected across
tion; and indicating means connected in series with said
a corresponding recti?er cell in a corresponding recti?er
primary winding to form a series circuit across said recti
leg; a blocking recti?er in series with each of said second
?er leg for sensing changes in the impedance of said pri
ary windings for normally maintaining said winding in a
mary winding in response to a flow of current in said
substantially open circuit condition; and a plurality of
secondary windings during the blocking half cycle of said
indicating means, each in series with its corresponding
recti?er leg, said indicating means including a resistor in
primary winding to form a series circuit, said series
series with said primary winding and a neon indicating
circuit being connected across its corresponding recti?er
lamp connected across said series resistor.
leg for responding to changes in the impedance of its
13. In combination with a recti?er leg having a plural
corresponding primary winding in response to current 55 ity of recti?er cells connected in series, means :for detect
flow in said corresponding secondary windings during the
ing the ‘failure of at least one of said recti?er cells compris
blocking half cycle of said recti?er bank.
ing: a transformer having a primary winding connected
9. The combination of claim 8 which further includes
across said recti?er leg and a plurality of secondary wind
remote indicating means connected in series with the
ings, said secondary windings each being connected across
primary winding of each of said transformers to render
a corresponding recti?er cell; a ‘blocking recti?er in series
said remote indicating means dependent upon changes
with each of said ‘secondary windings for normally main
in the impedance of any primary winding for remotely
taining said windings in a substantially open circuit con
indicating the (failure of any recti?er cell.
dition; indicating means connected in series with said
10. In combination with a recti?er leg having a plural
primary winding to form a series circuit providing prede
ity oi recti?er cells connected in series and a balancing
termined voltage drops across said primary winding and
resistor connected in parallel with each of said recti?er
said indicating means during normal operation of the rec
cells, means for detecting the failure ‘of at least one of
ti?er leg; the shorting of a recti?er cell operating to de
said recti?er cells comprising: a transformer having a
crease the voltage drop across said primary winding and
primary winding and a plurality of secondary windings,
correspondingly to increase the voltage drop across said
said secondary windings each being connected across a 70 indicating means whereby said voltage drop across said in
corresponding recti?er cell and its corresponding balanc
dicating means exceeds the voltage required to actuate said
ing resistor; a resistor connected in series with said pri
indicating means, said indicating means including a re—
mary winding to form a series circuit, said series circuit
sister in series with said primary winding and a neon
being connected across said recti?er leg and providing
indicating lamp connected across said series resistor.
predetermined voltage drops across said primary winding
14. In combination with a recti?er leg having a plural
3,099,828
9
ity of recti?er cells connected in series, a fuse connected
in series with said recti?er leg, means for detecting the
10
to effect an indication of a failed recti?er only when said
fuse is intact ‘and having a second branch connected be
tween said primary winding terminal and the other ter
minal of said fuse to eifect an indication of a failed recti
transformer having a primary winding connected across
said recti?er leg and a plurality of secondary windings, 5 ?er irrespective of the condition of said fuse.
said secondary windings each being connected across a
failure of at least one \of said recti?er cells comprising a
corresponding recti?er cell; a blocking recti?er in series
With each of said secondary windings for normally main
taining said windings in a substantially open circuit condi
tion, indicating means connected in series with said pri 10
mary winding and response to changes in impedance
of said primary winding due to current flow in at least
:one of said secondary windings for effecting an indication
Otf a failed recti?er cell; said indicating means having a
?rst branch connected between a terminal of said primary 15
winding and the common terminal of said fuse and leg
References Cited in the ?le of this patent
UNITED STATES PATENTS
1,867,419
, 2,447,658
Peek _______________ __ July 12, 1932
Manbury et al _________ __ Aug. 24, 1948
2,492,343
Zavales ______________ __ Dec. 27, 1949
2,568,172
2,678,418
Spencer _____________ __ Sept. 18, 1951
Black ______________ __ May 11, 1954
2,917,697
2,930,961
Diebold _____________ __ Dec. 15, 1959
Lezan ______________ __ Mar. 29, 1960
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